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Message-ID: <00000000000082477205811c029c@google.com>
Date:   Mon, 04 Feb 2019 18:03:04 -0800
From:   syzbot <syzbot+a3accb352f9c22041cfa@...kaller.appspotmail.com>
To:     bcrl@...ck.org, linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: possible deadlock in io_submit_one

Hello,

syzbot found the following crash on:

HEAD commit:    5eeb63359b1e Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17906f64c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e0064f906afee10
dashboard link: https://syzkaller.appspot.com/bug?extid=a3accb352f9c22041cfa
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=156479f8c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=128c75c4c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3accb352f9c22041cfa@...kaller.appspotmail.com

=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
5.0.0-rc4+ #56 Not tainted
-----------------------------------------------------
syz-executor263/8874 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
00000000c469f622 (&ctx->fd_wqh){....}, at: spin_lock  
include/linux/spinlock.h:329 [inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: aio_poll fs/aio.c:1772 [inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: __io_submit_one fs/aio.c:1875  
[inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: io_submit_one+0xedf/0x1cf0  
fs/aio.c:1908

and this task is already holding:
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq  
include/linux/spinlock.h:354 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll  
fs/aio.c:1771 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one  
fs/aio.c:1875 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at:  
io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908
which would create a new lock dependency:
  (&(&ctx->ctx_lock)->rlock){..-.} -> (&ctx->fd_wqh){....}

but this new dependency connects a SOFTIRQ-irq-safe lock:
  (&(&ctx->ctx_lock)->rlock){..-.}

... which became SOFTIRQ-irq-safe at:
   lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
   __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
   _raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160
   spin_lock_irq include/linux/spinlock.h:354 [inline]
   free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
   percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline]
   percpu_ref_put include/linux/percpu-refcount.h:301 [inline]
   percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
   percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158
   __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
   rcu_do_batch kernel/rcu/tree.c:2452 [inline]
   invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
   rcu_process_callbacks+0x928/0x1390 kernel/rcu/tree.c:2754
   __do_softirq+0x266/0x95a kernel/softirq.c:292
   invoke_softirq kernel/softirq.c:373 [inline]
   irq_exit+0x180/0x1d0 kernel/softirq.c:413
   exiting_irq arch/x86/include/asm/apic.h:536 [inline]
   smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
   apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
   native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:57
   arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
   default_idle_call+0x36/0x90 kernel/sched/idle.c:93
   cpuidle_idle_call kernel/sched/idle.c:153 [inline]
   do_idle+0x386/0x570 kernel/sched/idle.c:262
   cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
   rest_init+0x245/0x37b init/main.c:442
   arch_call_rest_init+0xe/0x1b
   start_kernel+0x808/0x841 init/main.c:740
   x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
   x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
   secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

to a SOFTIRQ-irq-unsafe lock:
  (&ctx->fault_pending_wqh){+.+.}

... which became SOFTIRQ-irq-unsafe at:
...
   lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
   __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
   _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
   spin_lock include/linux/spinlock.h:329 [inline]
   userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
   __fput+0x2df/0x8d0 fs/file_table.c:278
   ____fput+0x16/0x20 fs/file_table.c:309
   task_work_run+0x14a/0x1c0 kernel/task_work.c:113
   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
   exit_to_usermode_loop+0x273/0x2c0 arch/x86/entry/common.c:166
   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
   do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
   &(&ctx->ctx_lock)->rlock --> &ctx->fd_wqh --> &ctx->fault_pending_wqh

  Possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&ctx->fault_pending_wqh);
                                local_irq_disable();
                                lock(&(&ctx->ctx_lock)->rlock);
                                lock(&ctx->fd_wqh);
   <Interrupt>
     lock(&(&ctx->ctx_lock)->rlock);

  *** DEADLOCK ***

1 lock held by syz-executor263/8874:
  #0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq  
include/linux/spinlock.h:354 [inline]
  #0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll  
fs/aio.c:1771 [inline]
  #0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one  
fs/aio.c:1875 [inline]
  #0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at:  
io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908

the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (&(&ctx->ctx_lock)->rlock){..-.} {
    IN-SOFTIRQ-W at:
                     lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                     __raw_spin_lock_irq  
include/linux/spinlock_api_smp.h:128 [inline]
                     _raw_spin_lock_irq+0x60/0x80  
kernel/locking/spinlock.c:160
                     spin_lock_irq include/linux/spinlock.h:354 [inline]
                     free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
                     percpu_ref_put_many include/linux/percpu-refcount.h:285  
[inline]
                     percpu_ref_put include/linux/percpu-refcount.h:301  
[inline]
                     percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123  
[inline]
                     percpu_ref_switch_to_atomic_rcu+0x3e7/0x520  
lib/percpu-refcount.c:158
                     __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
                     rcu_do_batch kernel/rcu/tree.c:2452 [inline]
                     invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
                     rcu_process_callbacks+0x928/0x1390  
kernel/rcu/tree.c:2754
                     __do_softirq+0x266/0x95a kernel/softirq.c:292
                     invoke_softirq kernel/softirq.c:373 [inline]
                     irq_exit+0x180/0x1d0 kernel/softirq.c:413
                     exiting_irq arch/x86/include/asm/apic.h:536 [inline]
                     smp_apic_timer_interrupt+0x14a/0x570  
arch/x86/kernel/apic/apic.c:1062
                     apic_timer_interrupt+0xf/0x20  
arch/x86/entry/entry_64.S:807
                     native_safe_halt+0x2/0x10  
arch/x86/include/asm/irqflags.h:57
                     arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
                     default_idle_call+0x36/0x90 kernel/sched/idle.c:93
                     cpuidle_idle_call kernel/sched/idle.c:153 [inline]
                     do_idle+0x386/0x570 kernel/sched/idle.c:262
                     cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
                     rest_init+0x245/0x37b init/main.c:442
                     arch_call_rest_init+0xe/0x1b
                     start_kernel+0x808/0x841 init/main.c:740
                     x86_64_start_reservations+0x29/0x2b  
arch/x86/kernel/head64.c:470
                     x86_64_start_kernel+0x77/0x7b  
arch/x86/kernel/head64.c:451
                     secondary_startup_64+0xa4/0xb0  
arch/x86/kernel/head_64.S:243
    INITIAL USE at:
                    lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128  
[inline]
                    _raw_spin_lock_irq+0x60/0x80  
kernel/locking/spinlock.c:160
                    spin_lock_irq include/linux/spinlock.h:354 [inline]
                    free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
                    percpu_ref_put_many include/linux/percpu-refcount.h:285  
[inline]
                    percpu_ref_put include/linux/percpu-refcount.h:301  
[inline]
                    percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123  
[inline]
                    percpu_ref_switch_to_atomic_rcu+0x3e7/0x520  
lib/percpu-refcount.c:158
                    __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
                    rcu_do_batch kernel/rcu/tree.c:2452 [inline]
                    invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
                    rcu_process_callbacks+0x928/0x1390 kernel/rcu/tree.c:2754
                    __do_softirq+0x266/0x95a kernel/softirq.c:292
                    invoke_softirq kernel/softirq.c:373 [inline]
                    irq_exit+0x180/0x1d0 kernel/softirq.c:413
                    exiting_irq arch/x86/include/asm/apic.h:536 [inline]
                    smp_apic_timer_interrupt+0x14a/0x570  
arch/x86/kernel/apic/apic.c:1062
                    apic_timer_interrupt+0xf/0x20  
arch/x86/entry/entry_64.S:807
                    native_safe_halt+0x2/0x10  
arch/x86/include/asm/irqflags.h:57
                    arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
                    default_idle_call+0x36/0x90 kernel/sched/idle.c:93
                    cpuidle_idle_call kernel/sched/idle.c:153 [inline]
                    do_idle+0x386/0x570 kernel/sched/idle.c:262
                    cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
                    start_secondary+0x404/0x5c0 arch/x86/kernel/smpboot.c:271
                    secondary_startup_64+0xa4/0xb0  
arch/x86/kernel/head_64.S:243
  }
  ... key      at: [<ffffffff8a5760a0>] __key.51972+0x0/0x40
  ... acquired at:
    lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
    _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
    spin_lock include/linux/spinlock.h:329 [inline]
    aio_poll fs/aio.c:1772 [inline]
    __io_submit_one fs/aio.c:1875 [inline]
    io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
    __do_sys_io_submit fs/aio.c:1953 [inline]
    __se_sys_io_submit fs/aio.c:1923 [inline]
    __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923
    do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe


the dependencies between the lock to be acquired
  and SOFTIRQ-irq-unsafe lock:
  -> (&ctx->fault_pending_wqh){+.+.} {
     HARDIRQ-ON-W at:
                       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                       __raw_spin_lock include/linux/spinlock_api_smp.h:142  
[inline]
                       _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
                       spin_lock include/linux/spinlock.h:329 [inline]
                       userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
                       __fput+0x2df/0x8d0 fs/file_table.c:278
                       ____fput+0x16/0x20 fs/file_table.c:309
                       task_work_run+0x14a/0x1c0 kernel/task_work.c:113
                       tracehook_notify_resume include/linux/tracehook.h:188  
[inline]
                       exit_to_usermode_loop+0x273/0x2c0  
arch/x86/entry/common.c:166
                       prepare_exit_to_usermode arch/x86/entry/common.c:197  
[inline]
                       syscall_return_slowpath arch/x86/entry/common.c:268  
[inline]
                       do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
                       entry_SYSCALL_64_after_hwframe+0x49/0xbe
     SOFTIRQ-ON-W at:
                       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                       __raw_spin_lock include/linux/spinlock_api_smp.h:142  
[inline]
                       _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
                       spin_lock include/linux/spinlock.h:329 [inline]
                       userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
                       __fput+0x2df/0x8d0 fs/file_table.c:278
                       ____fput+0x16/0x20 fs/file_table.c:309
                       task_work_run+0x14a/0x1c0 kernel/task_work.c:113
                       tracehook_notify_resume include/linux/tracehook.h:188  
[inline]
                       exit_to_usermode_loop+0x273/0x2c0  
arch/x86/entry/common.c:166
                       prepare_exit_to_usermode arch/x86/entry/common.c:197  
[inline]
                       syscall_return_slowpath arch/x86/entry/common.c:268  
[inline]
                       do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
                       entry_SYSCALL_64_after_hwframe+0x49/0xbe
     INITIAL USE at:
                      lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                      __raw_spin_lock include/linux/spinlock_api_smp.h:142  
[inline]
                      _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
                      spin_lock include/linux/spinlock.h:329 [inline]
                      userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
                      userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
                      __vfs_read+0x116/0x8c0 fs/read_write.c:416
                      vfs_read+0x194/0x3e0 fs/read_write.c:452
                      ksys_read+0xea/0x1f0 fs/read_write.c:578
                      __do_sys_read fs/read_write.c:588 [inline]
                      __se_sys_read fs/read_write.c:586 [inline]
                      __x64_sys_read+0x73/0xb0 fs/read_write.c:586
                      do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
                      entry_SYSCALL_64_after_hwframe+0x49/0xbe
   }
   ... key      at: [<ffffffff8a575ee0>] __key.44851+0x0/0x40
   ... acquired at:
    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
    _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
    spin_lock include/linux/spinlock.h:329 [inline]
    userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
    userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
    __vfs_read+0x116/0x8c0 fs/read_write.c:416
    vfs_read+0x194/0x3e0 fs/read_write.c:452
    ksys_read+0xea/0x1f0 fs/read_write.c:578
    __do_sys_read fs/read_write.c:588 [inline]
    __se_sys_read fs/read_write.c:586 [inline]
    __x64_sys_read+0x73/0xb0 fs/read_write.c:586
    do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> (&ctx->fd_wqh){....} {
    INITIAL USE at:
                    lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
                    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128  
[inline]
                    _raw_spin_lock_irq+0x60/0x80  
kernel/locking/spinlock.c:160
                    spin_lock_irq include/linux/spinlock.h:354 [inline]
                    userfaultfd_ctx_read fs/userfaultfd.c:1036 [inline]
                    userfaultfd_read+0x27a/0x1940 fs/userfaultfd.c:1198
                    __vfs_read+0x116/0x8c0 fs/read_write.c:416
                    vfs_read+0x194/0x3e0 fs/read_write.c:452
                    ksys_read+0xea/0x1f0 fs/read_write.c:578
                    __do_sys_read fs/read_write.c:588 [inline]
                    __se_sys_read fs/read_write.c:586 [inline]
                    __x64_sys_read+0x73/0xb0 fs/read_write.c:586
                    do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
                    entry_SYSCALL_64_after_hwframe+0x49/0xbe
  }
  ... key      at: [<ffffffff8a575e20>] __key.44854+0x0/0x40
  ... acquired at:
    lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
    _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
    spin_lock include/linux/spinlock.h:329 [inline]
    aio_poll fs/aio.c:1772 [inline]
    __io_submit_one fs/aio.c:1875 [inline]
    io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
    __do_sys_io_submit fs/aio.c:1953 [inline]
    __se_sys_io_submit fs/aio.c:1923 [inline]
    __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923
    do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe


stack backtrace:
CPU: 1 PID: 8874 Comm: syz-executor263 Not tainted 5.0.0-rc4+ #56
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  print_bad_irq_dependency kernel/locking/lockdep.c:1573 [inline]
  check_usage.cold+0x60f/0x940 kernel/locking/lockdep.c:1605
  check_irq_usage kernel/locking/lockdep.c:1661 [inline]
  check_prev_add_irq kernel/locking/lockdep_states.h:8 [inline]
  check_prev_add kernel/locking/lockdep.c:1871 [inline]
  check_prevs_add kernel/locking/lockdep.c:1979 [inline]
  validate_chain kernel/locking/lockdep.c:2350 [inline]
  __lock_acquire+0x1f47/0x4700 kernel/locking/lockdep.c:3338
  lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
  __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
  _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
  spin_lock include/linux/spinlock.h:329 [inline]
  aio_poll fs/aio.c:1772 [inline]
  __io_submit_one fs/aio.c:1875 [inline]
  io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
  __do_sys_io_submit fs/aio.c:1953 [inline]
  __se_sys_io_submit fs/aio.c:1923 [inline]
  __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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